<tt>[3.10+]</tt> The space between the {{nowrap|"<tt>#</tt>"}} symbol and the comment is no longer required.

+

{{v|3.10+}}The space between the {{nowrap|"<tt>#</tt>"}} symbol and the comment is no longer required.

=== MENU ===

=== MENU ===

Line 62:

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<code>'''MENU''' ''any string''</code>

<code>'''MENU''' ''any string''</code>

−

<tt>[3.00+]</tt> A directive for the Simple [[Menu]] system, treated as a comment outside the menu.

+

{{v|3.00+}}A directive for the Simple [[Menu]] system, treated as a comment outside the menu.

See also [[doc/menu]].txt.

See also [[doc/menu]].txt.

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Multiple uses will result in an override.

Multiple uses will result in an override.

−

<tt>[3.85+]</tt> If no configuration file is found, or neither DEFAULT nor UI entries are present in the config file, then an error message is displayed and the {{nowrap|"<tt>boot:</tt>"}} prompt is shown.

+

{{v|3.85+}}If no configuration file is found, or neither DEFAULT nor UI entries are present in the config file, then an error message is displayed and the {{nowrap|"<tt>boot:</tt>"}} prompt is shown.

−

<font size=1>Note: <tt>[-3.84]</tt> If no configuration file was found, or no DEFAULT entry was present in the configuration file, the default kernel name was "linux", with no options.</font size>

+

<font size=1>Note: {{v|-3.84}}If no configuration file was found, or no DEFAULT entry was present in the configuration file, the default kernel name was "linux", with no options.</font size>

<!-- -->

<!-- -->

−

<!-- <font size=1><tt>[-3.84]</tt> The default LABEL is "linux", but you can change this with the "DEFAULT" keyword.</font size> -->

+

<!-- <font size=1>{{v|-3.84}}The default LABEL is "linux", but you can change this with the "DEFAULT" keyword.</font size> -->

−

<!-- <font size=1><tt>[-3.84]</tt> At boot time, by default, the kernel will be loaded from the image named "linux" on the boot disk. -->

+

<!-- <font size=1>{{v|-3.84}}At boot time, by default, the kernel will be loaded from the image named "linux" on the boot disk. -->

<!-- -->

<!-- -->

Line 134:

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Prior to version 3.32, this would be transformed to a {{nowrap|DOS-compatible}} format of {{nowrap|"8.3"}} with a restricted character set.

Prior to version 3.32, this would be transformed to a {{nowrap|DOS-compatible}} format of {{nowrap|"8.3"}} with a restricted character set.

<!-- -->

<!-- -->

−

<!-- <font size=1><tt>[-3.84]</tt> The default LABEL is "linux", but you can change this with the "DEFAULT" keyword.</font size> -->

+

<!-- <font size=1>{{v|-3.84}}The default LABEL is "linux", but you can change this with the "DEFAULT" keyword.</font size> -->

−

<!-- <font size=1><tt>[-3.84]</tt> At boot time, by default, the kernel will be loaded from the image named "linux" on the boot disk. -->

+

<!-- <font size=1>{{v|-3.84}}At boot time, by default, the kernel will be loaded from the image named "linux" on the boot disk. -->

−

<!-- <font size=1>Note: <tt>[-3.84]</tt> If no configuration file was found, or no DEFAULT entry was present in the configuration file, the default kernel name was "linux", with no options.</font size> -->

+

<!-- <font size=1>Note: {{v|-3.84}}If no configuration file was found, or no DEFAULT entry was present in the configuration file, the default kernel name was "linux", with no options.</font size> -->

<!-- -->

<!-- -->

Line 147:

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== DUAL-PURPOSE DIRECTIVES ==

== DUAL-PURPOSE DIRECTIVES ==

−

<tt>[-4.xx]</tt> Use of any of the {{nowrap|DUAL-PURPOSE DIRECTIVES}} as [[#GLOBAL_DIRECTIVES_-_MAIN|{{nowrap|GLOBAL DIRECTIVES}}]] is discouraged if there will be any non-Linux images loaded, as <u>all</u> images will get these, including those manually entered at the {{nowrap|"<tt>boot:</tt>"}} prompt.

+

{{v|-4.xx}}Use of any of the {{nowrap|DUAL-PURPOSE DIRECTIVES}} as [[#GLOBAL_DIRECTIVES_-_MAIN|{{nowrap|GLOBAL DIRECTIVES}}]] is discouraged if there will be any non-Linux images loaded, as <u>all</u> images will get these, including those manually entered at the {{nowrap|"<tt>boot:</tt>"}} prompt.

=== APPEND ===

=== APPEND ===

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Line 179:

<code>'''SYSAPPEND''' ''bitmask''</code>

<code>'''SYSAPPEND''' ''bitmask''</code>

−

<tt>[IPAPPEND: PXELINUX only; SYSAPPEND: 5.10+]</tt> <br />

+

{{v|IPAPPEND: PXELINUX only; SYSAPPEND: 5.10+}}<br />

The SYSAPPEND option, introduced in Syslinux 5.10, is an enhancement of a previous IPAPPEND option which was only available on PXELINUX.

The SYSAPPEND option, introduced in Syslinux 5.10, is an enhancement of a previous IPAPPEND option which was only available on PXELINUX.

'''DMI''': <tt>[5.10+]</tt> The following strings are derived from DMI/SMBIOS information if available:

+

'''DMI''': {{v|5.10+}}The following strings are derived from DMI/SMBIOS information if available:

<pre>

<pre>

Bit String Significance

Bit String Significance

Line 281:

Line 281:

</pre>

</pre>

−

'''0x40000''': <tt>[5.10+]</tt> An option of the following format should be generated, appending a filesystem UUID string to the kernel command line; for {{nowrap|1=EXT2/3/4}}, the resulting string will be the typical filesystem UUID; for {{nowrap|1=FAT12/16/32}}, the resulting string will be the 32-bit filesystem serial number (e.g. DA1A-0B2E):

+

'''0x40000''': {{v|5.10+}}An option of the following format should be generated, appending a filesystem UUID string to the kernel command line; for {{nowrap|1=EXT2/3/4}}, the resulting string will be the typical filesystem UUID; for {{nowrap|1=FAT12/16/32}}, the resulting string will be the 32-bit filesystem serial number (e.g. DA1A-0B2E):

The PXE protocol does not provide any means for specifiying or using a command line or initrd.

The PXE protocol does not provide any means for specifiying or using a command line or initrd.

See also [[Pxechn.c32]].

See also [[Pxechn.c32]].

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<code>'''LOCALBOOT''' ''type''</code>

<code>'''LOCALBOOT''' ''type''</code>

−

<tt>[PXELINUX 1.53+; ISOLINUX 3.10+; SYSLINUX 3.70+]</tt> <br />

+

{{v|PXELINUX 1.53+; ISOLINUX 3.10+; SYSLINUX 3.70+}}<br />

Attempt a different local boot method.

Attempt a different local boot method.

Specifying LOCALBOOT instead of a KERNEL option means that invoking this particular label will cause a local disk boot instead of booting a kernel.

Specifying LOCALBOOT instead of a KERNEL option means that invoking this particular label will cause a local disk boot instead of booting a kernel.

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<br />''type'' <tt>-1</tt> (minus one)&nbsp;: Cause the boot loader to report failure to the BIOS, which, on recent BIOSes, should mean that the next boot device in the boot sequence should be activated.

<br />''type'' <tt>-1</tt> (minus one)&nbsp;: Cause the boot loader to report failure to the BIOS, which, on recent BIOSes, should mean that the next boot device in the boot sequence should be activated.

<tt>[PXELINUX]</tt> ''type'' <tt>4</tt>&nbsp;: Perform a local boot with the Universal Network Driver Interface (UNDI) driver still resident in memory.

+

{{v|PXELINUX}}''type'' <tt>4</tt>&nbsp;: Perform a local boot with the Universal Network Driver Interface (UNDI) driver still resident in memory.

−

<tt>[PXELINUX]</tt> ''type'' <tt>5</tt>&nbsp;: Perform a local boot with the entire PXE stack, including the UNDI driver, still resident in memory.

+

{{v|PXELINUX}}''type'' <tt>5</tt>&nbsp;: Perform a local boot with the entire PXE stack, including the UNDI driver, still resident in memory.

<br />If you do not know what the UNDI or PXE stacks are, don't worry -- you don't want them, just specify {{nowrap|<tt>0</tt> (zero).}}

<br />If you do not know what the UNDI or PXE stacks are, don't worry -- you don't want them, just specify {{nowrap|<tt>0</tt> (zero).}}

−

<br /><tt>[ISOLINUX/SYSLINUX]</tt> The ''type'' specifies the local drive number to boot from; <tt>0x00</tt> is the primary floppy drive and <tt>0x80</tt> is the primary hard drive.

+

<br />{{v|ISOLINUX/SYSLINUX}}The ''type'' specifies the local drive number to boot from; <tt>0x00</tt> is the primary floppy drive and <tt>0x80</tt> is the primary hard drive.

<br />

<br />

Line 394:

Line 394:

<code>'''INITRD''' ''initrd_file''</code>

<code>'''INITRD''' ''initrd_file''</code>

−

<tt>[3.71+]</tt> An initrd can be specified in a separate statement (INITRD) instead of as part of the APPEND statement.

+

{{v|3.71+}}An initrd can be specified in a separate statement (INITRD) instead of as part of the APPEND statement.

This functionally appends {{nowrap|1="<tt>initrd=initrd_file</tt>"}} to the kernel command line.

This functionally appends {{nowrap|1="<tt>initrd=initrd_file</tt>"}} to the kernel command line.

Line 485:

Line 485:

<code>'''SENDCOOKIES''' ''bitmask''</code>

<code>'''SENDCOOKIES''' ''bitmask''</code>

−

<tt>[PXELINUX 5.10+]</tt> When downloading files over http, the SYSAPPEND strings are prepended with {{nowrap|"<tt>_Syslinux_</tt>"}} (the word "Syslinux" in between one underscore character on each side) and sent to the server as cookies.

+

{{v|PXELINUX 5.10+}}When downloading files over http, the SYSAPPEND strings are prepended with {{nowrap|"<tt>_Syslinux_</tt>"}} (the word "Syslinux" in between one underscore character on each side) and sent to the server as cookies.

The cookies are URL-encoded; whitespace is <u>not</u> replaced with underscore.

The cookies are URL-encoded; whitespace is <u>not</u> replaced with underscore.

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Line 497:

<code>'''PXERETRY''' ''n''</code>

<code>'''PXERETRY''' ''n''</code>

−

<tt>[PXELINUX 4.03+]</tt> Re-attempt ''n'' times to {{nowrap|find/retrieve/open}} a file before giving up.

+

{{v|PXELINUX 4.03+}}Re-attempt ''n'' times to {{nowrap|find/retrieve/open}} a file before giving up.

For web downloads, sometimes a mirror site will not be {{nowrap|fully synced}}.

For web downloads, sometimes a mirror site will not be {{nowrap|fully synced}}.

Line 508:

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<code>'''PATH''' ''mylibpath''</code>

<code>'''PATH''' ''mylibpath''</code>

−

<tt>[5.11+]</tt> Specify a space-separated list of directories to be searched when attempting to load modules.

+

{{v|5.11+}}Specify a space-separated list of directories to be searched when attempting to load modules.

This directive is useful for specifying the directories containing the {{nowrap|"lib*.c32"}} library files, as other modules may depend on these files but might not reside in the same directory.

This directive is useful for specifying the directories containing the {{nowrap|"lib*.c32"}} library files, as other modules may depend on these files but might not reside in the same directory.

Multiple instances will append additional paths.

Multiple instances will append additional paths.

−

<tt>[5.00-5.10]</tt> The list separator was previously a {{nowrap|colon ":"}} character.

Revision as of 08:34, 12 March 2017

Introduction

This document describes the configuration for the boot behavior and user experience of Syslinux boot loaders, the format of "Display" files and the boot prompt behavior.

Note that the configuration file is not completely decoded.
Syntax different from the one described here may still work correctly in some version of Syslinux, but may break in another (future) one.

The configuration file is a text file in either UNIX or DOS format, containing one or more of the keywords listed below.
Keywords are case insensitive.
Upper case is used here to indicate a word should be typed verbatim.

Blank lines are ignored.

Here is a simple example of a Syslinux configuration file, with one entry to boot a Linux kernel:

[4.00+] In each searched-for directory,
SYSLINUX searches first for
extlinux.conf and then for
syslinux.cfg before falling back to the next directory.

[-4.02] ISOLINUX uses
isolinux.cfg as config file name,
searching first in
"/boot/isolinux/" [2.00+] , then in
"/isolinux/"
and then in "/".

[4.03+] ISOLINUX searches for
isolinux.cfg and then for
syslinux.cfg in
"/boot/isolinux/"
before searching for the same files in
"/isolinux/",
"/boot/syslinux/",
"/syslinux/", and
"/", in this order.

Since version 4.03, the resulting behavior is that the same
"/[[boot/]syslinux/]syslinux.cfg"
file can optionally be used for
SYSLINUX / EXTLINUX / ISOLINUX,
while specific isolinux.cfg
and/or extlinux.conf files would take precedence if present.

Since version 4.03, the resulting behavior is that
any of the respective config files (or even all of them)
— namely
isolinux.cfg, and/or
extlinux.conf, and/or
syslinux.cfg —
can optionally be located together in the same
"/[[boot/]syslinux/]"
directory.

UEFI

SYSLINUX
defaults to searching for
the configuration file in the installed directory, where
syslinux.efi
is located and containing also its corresponding
" ldlinux.* "
file.

[6.04+] In each searched-for directory,
SYSLINUX searches first for
either:

syslia32.cfg when booting in EFI_ia32 mode

syslx64.cfg when booting in EFI_x64 mode

and finally
SYSLINUX searches for syslinux.cfg
before falling back to the next directory.

The first configuration file that is found
stops the search and
the configuration file is parsed / used.

Note that syslinux.efi could be optionally renamed.

Working directory

Note: In the following paragraphs, the "/" directory represents the root of the filesystem in which Syslinux (in its several variants) is (going to be) installed.

When booting, the initial working directory for
SYSLINUX / ISOLINUX
will be the directory containing the initial configuration file.

[5.00+] If no initial configuration file is found, then
SYSLINUX / ISOLINUX
defaults to the install-time working
directory (where " ldlinux.* " is located).

When booting, the initial working directory for
PXELINUX
will be the parent directory of pxelinux.0
unless overridden with DHCP option 210.
If no configuration file is found, then
PXELINUX
will start a timer to
reboot the system in an attempt to restart the boot process and
resolve a possible transient issue.

All (paths to) file names inside the configuration file are relative to the Working Directory,
unless preceded with a slash.
This is also valid for the command line interface.

MENU

INCLUDE

Insert the contents of another file, at this point in the configuration file.
Files can currently be nested up to 16 levels deep, but it is not guaranteed that more than 8 levels will be supported in the future.

DEFAULT

Set the default command line (which often references a LABEL).
If Syslinux boots automatically, it will act just as if the commands after DEFAULT had been typed in at the "boot:" prompt.
Multiple uses will result in an override.

[3.85+] If no configuration file is found, or neither DEFAULT nor UI entries are present in the config file, then an error message is displayed and the "boot:" prompt is shown.

Note: [-3.84] If no configuration file was found, or no DEFAULT entry was present in the configuration file, the default kernel name was "linux", with no options.

Note: Earlier versions of SYSLINUX used to automatically append the string "auto" to whatever the user specified using the DEFAULT command.
As of version 1.54, this is no longer true, as it caused problems when using a shell as a substitute for "init".
You might want to include this option manually.

UI

UI overrides the PROMPT directive and takes precedence over the DEFAULT directive.
Therefore, if UI is used, the PROMPT directive is ignored and the UI command -- not the DEFAULT command -- is automatically launched:

LABEL

Begin a new LABEL clause.
If mylabel is entered as the kernel to boot, Syslinux should instead boot "image" (specified by a directive from #KERNEL-LIKE DIRECTIVES) with any specified #DUAL-PURPOSE DIRECTIVES being used instead of the global instance.

mylabel must be unique.
If not, the first instance is used, but might result in an error or undesired behavior.

mylabel ends at the first character that is not a non-white-space printable character and should be restricted to non-white-space typeable characters.

Prior to version 3.32, this would be transformed to a DOS-compatible format of "8.3" with a restricted character set.

DUAL-PURPOSE DIRECTIVES

[-4.xx] Use of any of the DUAL-PURPOSE DIRECTIVES as GLOBAL DIRECTIVES is discouraged if there will be any non-Linux images loaded, as all images will get these, including those manually entered at the "boot:" prompt.

APPEND

Add one or more options to the kernel command line.
These are added to both, automatic and manual boots.
The options are added at the very beginning of the kernel command line, usually permitting explicitly entered kernel options to override them.
This is the equivalent of the LILO "append" option.

Each APPEND statement shall not span multiple lines; it must be solely on a single line in the configuration file.

If you enter multiple APPEND statements in a single LABEL entry, only the last one will be used.

APPEND -

SYSAPPEND

[IPAPPEND: PXELINUX only; SYSAPPEND: 5.10+]
The SYSAPPEND option, introduced in Syslinux 5.10, is an enhancement of a previous IPAPPEND option which was only available on PXELINUX.

bitmask is interpreted as decimal format unless prefixed with "0x" for hexadecimal or "0" (zero) for octal.
The bitmask is an OR (sum) of the following integer options:

1: An option of the following format should be generated, based on the input from the DHCP/BOOTP or PXE boot server, and added to the kernel command line (see note below; empty for non-PXELINUX variants):

ip=<client-ip>:<boot-server-ip>:<gw-ip>:<netmask>

Note:
The use of option 1 is no substitute for running a DHCP client in the booted system and should instead only be used to seed the client for a request.
Without regular renewals, the lease acquired by the PXE BIOS will expire, making the IP address available for reuse by the DHCP server.

Note:
The use of this option is not recommended.
If you have to use it, it is probably an indication that your network configuration is broken.
Using just "ip=dhcp" on the kernel command line is a preferrable option, or, better yet, run dhcpcd/dhclient, from an initrd if necessary.

2: An option of the following format should be generated, in dash-separated hexadecimal with leading hardware type (same as for the configuration file; see "doc/pxelinux.txt"), and added to the kernel command line, allowing an initrd program to determine from which interface the system booted (empty for non-PXELINUX variants):

BOOTIF=<hardware-address-of-boot-interface>

4: An option of the following format should be generated, in lower case hexadecimal in the format normally used for UUIDs (same as for the configuration file; see "doc/pxelinux.txt") and added to the kernel command line:

If these strings contain white-space characters, they are replaced with underscores (_).

The system form factor value is a number defined in the SMBIOS specification ("System Enclosure or Chassis Types"), available at http://www.dmtf.org/ .
As of version 2.7.1 of the specification, the following values are defined:

0x40000: [5.10+] An option of the following format should be generated, appending a filesystem UUID string to the kernel command line; for EXT2/3/4, the resulting string will be the typical filesystem UUID; for FAT12/16/32, the resulting string will be the 32-bit filesystem serial number (e.g. DA1A-0B2E):

CONFIG

Load a new configuration file.
The new configuration file is read, the Working Directory is optionally changed (if specified via an optional second parameter), and then the new configuration file is parsed.

If new_WD is not specified, then the Current Working Directory is maintained, unchanged.

The Working Directory may be different from the path to the config file.

LOCALBOOT

[PXELINUX 1.53+; ISOLINUX 3.10+; SYSLINUX 3.70+]
Attempt a different local boot method.
Specifying LOCALBOOT instead of a KERNEL option means that invoking this particular label will cause a local disk boot instead of booting a kernel.
Values other than those documented may produce undesired results.

type-1 (minus one) : Cause the boot loader to report failure to the BIOS, which, on recent BIOSes, should mean that the next boot device in the boot sequence should be activated.

[PXELINUX]type0 (zero) : Perform a normal local boot.

[PXELINUX]type4 : Perform a local boot with the Universal Network Driver Interface (UNDI) driver still resident in memory.

[PXELINUX]type5 : Perform a local boot with the entire PXE stack, including the UNDI driver, still resident in memory.

If you do not know what the UNDI or PXE stacks are, don't worry -- you don't want them, just specify 0 (zero).

[ISOLINUX/SYSLINUX] The type specifies the local drive number to boot from; 0x00 is the primary floppy drive and 0x80 is the primary hard drive.

LABEL-ONLY DIRECTIVES

INITRD

[3.71+] An initrd can be specified in a separate statement (INITRD) instead of as part of the APPEND statement.
This functionally appends "initrd=initrd_file" to the kernel command line.

The features of the "initrd=" parameter are also valid for the INITRD directive.

The "initrd=" parameter supports multiple filenames separated by commas (i.e. "initrd=initrd_file1,initrd_file2") within a single instance.
This is mostly useful for initramfs, which can be composed of multiple separate cpio or cpio.gz archives.

Note: all initrd files except the last one are zero-padded to a 4K page boundary.
This should not affect initramfs.

Note: Only the last effective "initrd=" parameter is used for loading initrd files.

This option is "sticky" and it is not automatically reset when loading a new configuration file with the CONFIG command;
the SERIAL directive would need to be explicitly used so as to change (or reset) its prior values.

NOHALT

If flag_val is 1, do not halt the processor while idle.
Halting the processor while idle, significantly reduces the power consumption, but can cause poor responsiveness to the serial console, especially when using scripts to drive the serial console, as opposed to human interaction.

SENDCOOKIES

[PXELINUX 5.10+] When downloading files over http, the SYSAPPEND strings are prepended with "_Syslinux_" (the word "Syslinux" in between one underscore character on each side) and sent to the server as cookies.
The cookies are URL-encoded; whitespace is not replaced with underscore.

This command limits the cookies to be sent; 0 (zero) means no cookies.
The default is "-1" (minus one), meaning "send all cookies".

This option is "sticky" and it is not automatically reset when loading a new configuration file with the CONFIG command.

PATH

[5.11+] Specify a space-separated list of directories to be searched when attempting to load modules.
This directive is useful for specifying the directories containing the "lib*.c32" library files, as other modules may depend on these files but might not reside in the same directory.
Multiple instances will append additional paths.

TIMEOUT

If more than one label entry is available, this directive indicates how long to wait at the "boot:" prompt until booting automatically, in units of 1/10 s.

The timeout is cancelled as soon as the user types anything on the keyboard; the assumption being that the user will complete the command line already begun.

The timer is reset to timeout upon return from an unsuccessful attempt to boot or from a module.
A timeout of zero (the default) will disable the timeout completely.

Note: The maximum possible timeout value is 35996 (just under an hour).

When only one label entry is available, the initial timeout is ignored.
To avoid automatically and immediately booting the (only and default) entry, use "escape" keys while booting, or add "PROMPT 1" to the configuration file, or add at least one additional label entry.

TOTALTIMEOUT

Indicate how long to wait until booting automatically, in units of 1/10 s.
This timeout is not cancelled by user input, and can thus be used to deal with serial port glitches or "the user walked away" type of situations.
A timeout of zero (the default) will disable the timeout completely.

ONERROR

If a kernel image is not found (either due to it not existing, or because IMPLICIT is set), run the specified command.
The faulty command line is appended to the specified options, so if the ONERROR directive reads as:

ONERROR xyzzy plugh

... and the (faulty) command line as entered by the user was:

foo bar baz

... then Syslinux will execute the following command as if it had been entered by the user:

xyzzy plugh foo bar baz

PROMPT

If flag_val is 0 (default), do not display the "boot:" prompt, unless either the [Shift] or the [Alt] key is pressed, or unless either [Caps Lock] or [Scroll Lock] is set.
If flag_val is 1, always display the "boot:"prompt.

KBDMAP

Install a simple keyboard map.
The keyboard remapper used is very simplistic (it simply remaps the keycodes received from the BIOS, which means that only the key combinations relevant in the default layout -- usually U.S. English -- can be mapped) but should at least help people with QWERTZ or AZERTY keyboard layouts and the locations of "=" and "," (two special characters used heavily on the Linux kernel command line).

The included program, "keytab-lilo.pl" from the LILO distribution, can be used to create such keymaps.
The file "doc/keytab-lilo.txt" contains the documentation for this program.

Syslinux also ships a module named kbdmap.c32 which allows changing the keyboard mapping on the fly, making it possible to add a keyboard-selection menu and/or keyboard-selection labels from within the Syslinux configuration file.

FONT

Load a font in ".psf" format before displaying any output (except the copyright line, which is output as soon as the very first step of the boot loader itself is loaded).
Syslinux only loads the font onto the video card; if the .psf file contains a Unicode table, it is ignored.
This only works on EGA and VGA cards; hopefully it should do nothing on others.

When using the serial console, press [Ctrl-F][digit] to get to the help screens, e.g. [Ctrl-F][2] to get to the F2 screen.
For F10-F12, hit [Ctrl-F][A],[Ctrl-F][B],[Ctrl-F][C].
For compatibility with earlier versions, F10 can also be entered as [Ctrl-F][0].

DISPLAY file format

DISPLAY and function-key help files are text files in either DOS or UNIX format (i.e. with or without <CR>).
See also IsoLinux Mate to help with writing DISPLAY files under Windows (or under WINE).

In addition, the following special codes are interpreted:

Clear the screen and home the cursor

<FF> <FF> = <Ctrl-L> = ASCII 12

Note that the screen is filled with the current display color.

Specify background and foreground colors

<SI><bg><fg> <SI> = <Ctrl-O> = ASCII 15

Set the display colors to the specified background and foreground colors, where <bg> and <fg> are the 2 hex digits representing 1 byte, corresponding to the standard PC display attributes:

Display graphic from filename

<CAN>filename<newline> <CAN> = <Ctrl-X> = ASCII 24

If a VGA display is present, enter graphics mode and display the graphic included in the specified file.
The file format is an ad hoc format called LSS16.
The included Perl program, "ppmtolss16", can be used to produce these images.
This Perl program also includes the file format specification.

The image is displayed in 640x480, 16-color mode.
Once in graphics mode, the display attributes (set by <SI> code sequences) work slightly differently: the background color is ignored, and the foreground colors are the 16 colors specified in the image file.
For that reason, ppmtolss16 allows you to specify that certain colors should be assigned to specific color indices.

Color indices 0 and 7 in particular, should be chosen with care: 0 is the background color, and 7 is the color used for the text printed by Syslinux itself.

Return to text mode

<EM> <EM> = <Ctrl-Y> = ASCII 25

If we are currently in graphics mode, return to text mode.

Output printing modes

<DLE>..<ETB> <Ctrl-P>..<Ctrl-W> = ASCII 16-23

These codes can be used to select in which modes to print a certain part of the message file.
Each of these control characters selects a specific set of modes (text screen, graphics screen, serial port) for which the output is actually displayed: